I have tried to do it for my Mega 4 but I only achieve a white screen with slightly yellow borders.

I have done the following:

TOS 1.04SP burnt in 2 27C010 EPROMS. The original TOS .IMG file had been splitted in two files (HI and LO) using Hatari and Ppera ROMSPLIT.Because it will be in a Mega ST and there is lot of free space I have used two 32 PIN socket per chip. So the images are here:

My 260 was equipped with a pair of these. Still have them. They are 16k x8 IIRC.With only 512KB RAM, 200KB gone by TOS, 32KB gone by screen memory and Atari BASIC loaded it left me with less memory than my C64!

For the pin 45 jumper I ran it to the W2 jumper. I left W3 the way it was, and W4 is not populated. These are the settings for the rom size.

First run nothing happened. Then I switched the hi and lo eproms. Then it seems to come up like a normal Atari doing the disk seek, but then throws 8 bombs.

Am I missing anything? At first I thought maybe 2.06 doesn't work on the Mega ST2, only STE but found better info.

One thing that might be helpful is a copy of the actual, split, known working 2.06 images for a US Mega ST2? I saw that filling the EPROMs with FF's will break checksum -- but would that cause my error?

qq1975b wrote:All my Mega ST with TOS 2.06 have a little PCB over the CPU besides the EPROMs hack... I will take a picture later if I can.

Someone replied to me on another forum that the Mega ST2 series does indeed need the decoder logic to use the 2.06 firmware. I had run across descriptions of this in reference to the 520/1040 but not the ST2.

Tonight I tried to burn a pair of 1.04 eproms and mounted them all up, but it just white screens and reboots. I'm going to do some research to make sure the programmer isn't writing 0xFF to the remainder of the space on the chip.

I did. But I did a bit more research this morning and found that the instructions I used were only part of it. I had pins 1 tied to 32 31 and 30 on each 27C010, which basically feeds 5VDC from socket pin 28 into those pins. I had pin 2 (Address line 16) tied to jumper W2 which is the same as socket pin 22. But I didn't have pin 24 on eprom (output enable) pulled up and tied to GND. So I did this when I got home.

The result is the machine now boots with 4 bombs, then resets into 6 bombs. Progress I guess?

This may not be relevant, but I would like to acquire TOS 1.02, 1.06 and 2.06 from my current machines. I have a UK 1040STFM (stock), a UK 1040STE (upgraded to 4MB) and a UK 4MB Mega STE (stock). I already have these TOS images downloaded from somewhere, but would like to get the TOS images I own backed up just so I can say I've done it. Is there a decent guide to doing this? I have access from PC to the Mega STE hdd and can create floppy disks from there. I don't have a PC floppy drive though, so something I could put on the Mega STE then write to floppy for the other ST's would be helpful.

Very interesting thread! I also just recently started to poke around and learn about the STs myself. I'm like you, doing a lot of searching online to find my answers which are somewhat scattered around and some sources showcase solutions to your problem, but since a lot of them are old you wonder if there's a more recent and complete guide/method/solution available. I'm an Atari-rookie and entering the world of Atari in 2017, in this forum for example, you're surrounded by Atari veterans that have all that valuable information in their brains. So I find it very good that you're taking this upon yourself to compile a rather easy-to-follow guide, for people like myself, with the expertise provided by the wise veterans . TOS in itself also seems like its' own science, but luckily experienced atarians are sharing their knowledge. Fortunately the Atati community is one of the most helpful I've ever stumbled upon. I'm gonna follow this thread, cause I'm also curious on how I can infuse my two STe:s with a tailored OS that get the most of the machine as well as meeting my needs as a musician/graphist looking forward to incorporate the ST as one of my creative tools!